Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart of concern. A typical procedure involves the insertion of a catheter having a tip electrode at its distal end into a heart chamber.
A typical mapping or ablation catheter has an elongated catheter body comprising a flexible lumened tubing, a more distal section comprising another flexible lumened tubing, and a tip electrode at distal end of the second tubing. Bonding adhesive is applied to affix the tip electrode to the second tubing. As a tissue contact area of the catheter, the tip electrode is subjected to a variety of stresses and strains during mapping and ablation. Repeated exposure to axial and lateral loads can weaken the bond between the tip electrode and the catheter. As the distal-most component of a catheter and hence the last component of the catheter to exit the patient's body, extra care and attention is given to its attachment to the catheter as detachment of the tip electrode would be a significant safety breach for the patient. Many catheter designs make use of a primary adhesive bond supplemented by additional structural joints in the form of a puller wire attachment directly to the tip electrode. The tip electrode may also be tethered by a lead wire or thermocouple wires. However, design failure mode effects analysis (DFMEA) requires redundant safety structures to reduce the risk of detachment.
Conventional catheters may provide a safety line that is tied or attached to the tip electrode. Typically an eyelet or loop of stainless steel or the like is soldered to a distal end or stem of the tip electrode and a distal end of the safety line is fed through the eyelet and knotted. However, eyelets are expensive and very time-consuming to manufacture. Moreover, crimping, tie offs, and tight bends in the safety line around the eyelet and within the knot induce stress concentrations causing premature wear and tear which can significantly reduce the tensile load carrying capability of the safety line. Additionally, the eyelet-knot arrangement occupies precious space in the tight quarters of a distal tip.
Accordingly, it is desirable that a catheter provide a tip configuration that can better accommodate a safety line and reduce the stress and strain so the safety line can more fully utilize its tensile load carrying capability. It is also desirable that the tip configuration make more efficient use of the space in the distal tip while accommodating the safety line without interfering with the housing and function of other components of the distal tip.